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  1. duke37

    PSPICE rectified AC to voltage regulator

    Looks as if you have positive feedback not negative.
  2. duke37

    single phase induction motor in grinder

    The capacitor could be a start capacitor or a run capacitor. A start capacitor will be used on a larger motor. The motor should run without a capacitor if spun to start with no load. If there is no action at all, then you will have to go through the circuit from plug connection to plug...
  3. duke37

    Help needed Black & Decker TR0692 Toaster button will not remain engaged Help Please

    When you measure a diode in circuit, you are measuring both the diode and the circuit so you can get the wrong answer. The black box is a relay driven by 12V DC and capable of changeover switching of 6A or 15A depending on voltage. You may be able to hear it click.
  4. duke37

    Sliders

    The potentiometer will be labelled with a resistance and this should be seen between contacts at either end. There will be no change in this resistance when the slider is moved. The input/ground should be connected to the end contacts and the output to ground and the slider. If you get it...
  5. duke37

    Amplitude and Frequency

    The circuit in #45 is wrong, the capacitor will short out the signal, so did you get it to work? Chris suggests that the computer may provide some power to drive the microphone. You can check if this is present with a meter. If not then you will need some power supplied as in the earlier...
  6. duke37

    MOSFET connected in phase opposition

    Q2 has no method of turning it on so nothing should fail. Q1 and Q3 are driven by external signals. These should be timed correctly with a dead time between conduction phases, if these are derived from a computer, then the program must be verified before connection. I would prefer hardware...
  7. duke37

    Omnidirectional LED lightbulb is OK?

    I think this is rubbish. The energy needed to recast the aluminium will be dependant on the mass as Steve says. Also, the aluminium will oxidise during the melting so a portion will be lost, the oxidised aluminium has to be skimmed of the suface of the melt. The amount of oxidation will...
  8. duke37

    Omnidirectional LED lightbulb is OK?

    This looks like a reasonable solution. The area of heat sink will not vary much with the heat sink material if the conductivity is adaquate. For the same conductance, I believe that aluminium is lighter than copper, also, if the copper is insulated on one side it will be inhibited...
  9. duke37

    Supplying DC when appliance wants AC

    It all depends on the circuit inside the charger. It may use the AC to generate several voltage rails for electronic circuitry. The power supply you have could perhaps be modified by by-passing the rectification/smoothing parts but not if it is a switched mode supply. You would be better...
  10. duke37

    Frequency Lock Loop

    What about generating 20MHz, then doubling to 40MHz and tripling to 60MHz? Switching at the correct point in the 20MHz wave will let the output change smoothly.
  11. duke37

    MOSFET connected in phase opposition

    I do not know what the circuit is supposed to do but Q2 should be a p-channel mosfet not a n-channel.
  12. duke37

    Two FM circuits

    The circuits are similar. Circuit 1 has AF and RF power supply bypass, this should be be included in Cir2 Circuit 2 has a capacitor in series with the aerial, this is good. The 2N3904 may be a better switch so the efficiency of Cir1 could be higher.
  13. duke37

    stop/tail led problems

    Faulty operation of a lamp cluster is often due to poor earth so that the cluster is earthed through other lights. You say you have a resistor between light and earth, if this resistor carries the current for more than one light, it is wrong. A circuit diagram is worth a thousand words.
  14. duke37

    Does anyone know of a modern capacitor with these values

    CR301 looks like a low voltage, low current bridge running at mains frequency. Four 1N4007 would romp away here.
  15. duke37

    Does anyone know of a modern capacitor with these values

    It is not easy to read the schematic. The diodes are shown as 1N538. The data for these seems to vary. They may be 100V 250mA.They are available on Google. I do not know what this thing does but if the frequency is not over, say, 10kHz then 1N4007 would be the cheapest when bought in bulk.
  16. duke37

    Amplitude and Frequency

    Try the microphone direct to the computer (through a 100n capacitor), you may not need an amplifier. A 555 will not handle a lot of power. The resistors and capacitor are there to set the frequency. The software which solo2racr recommends seems to do all that you want including replacing...
  17. duke37

    Wien Bridge Oscillator

    A Wien bridge oscillator needs an amplifier with a gain of three. Less gain than this will not oscillate. More gain than this and the oscillation will grow until it is limited in some way. The limiting will distort the sine wave so to get a good sine wave, the gain needs to be set just...
  18. duke37

    Amplitude and Frequency

    Frequency and pitch are the same thing. The frequency will be determined by an oscillator, in your case, the 555. Output level (amplitude) will not affect the pitch. The 555 will not be able to ouput much more than a mad mosquito. You will need a power amplifier to get sufficient power...
  19. duke37

    Series wound motor, what controls the top RPM?

    I have often wondered about this question. Most of the series wound motors are run on AC so there is a current limit due to the inductance of the windings. I have thought about trying an electric drill running on rectified AC and see if the speed goes up.
  20. duke37

    Amplitude and Frequency

    If you keep the input to less than 6V AC, the speaker should be OK.
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